Back then, the animals experienced short periods of higher-temperature climate in the midst of the (last) ice age. Large mammals in what is now the Arctic thrived and alternatively did not thrive during these periods. After the cycles and the ice age ended, and were followed by the spread of peatlands and heightening sea levels, animals became separated from one another. This habitat fragmentation contributed to their extinction, according to a release.

The study involved radiocarbon-dating fossils from mammals weighing more than 100 pounds, found on Alaska's North Slope, an area of tundra between the Brooks Range and the Arctic Ocean, said the release.

The information gleaned was compared (in terms of ages and abundances) to records of the climate change in the past 40,000 years, confirmed a release.

"We wanted to know how these large animals responded to the rapid climatic changes that characterized that period of Earth's history," Daniel Mann, at UAF, said in the release. "To do this, we tested a hypothesis suggested by (retired) UAF paleontologist Dale Guthrie that megafaunal populations experienced boom-and-bust cycles during the ice age as the vegetation tracked climate change."

As it happens, the 20-year UAF and UC study indicates that communities of animals and plants during the ice age were highly variable, much more so than they have been in the last 12,000 years of today's climate, said the release.

In particular, the scientists noted that the study is yet another factor showing that if we are to preserve current-day Arctic species, it's important to keep their habitats connected. "As human populations grow, patches of suitable habitat for many species are becoming increasingly isolated from each other," said Beth Shapiro of the University of California Santa Cruz, in the release. "If we are to preserve these species, we will need to devise strategies that allow these populations to remain somehow connected."

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